The present invention pertains to a valve stem assembly which is adapted to make a perfect seal with a rim upon which a tubeless tire is to fitted.
A variety of valve stem assemblies have been known heretofore but, despite the relative simplicity of such assemblies, it has been found that they are rather expensive to manufacture and often depend for their effectiveness upon a rubber-to-metal bond which is often difficult to maintain.
In order to avoid the difficulty and expense involved with those valve assemblies which require a rubber-to-metal bond, a particular valve stem assembly has been developed involving the replacement of many of the expensive metal parts with molded plastic parts. As an example of such a molded valve assembly, reference may be made to U.S. Pat. No. 3,032,091.
Whatever the merits of the molded plastic valve assembly described in the aforesaid patent, it has been found that superior results can accomplished by a different approach to the arrangement of the parts of such a plastic valve assembly; that is, to an approach which makes it extremely difficult to remove the valve assembly once it has been fitted or sealed with the tire rim.
Another object of the present invention is to provide a molded plastic valve assembly that is adapted not only to make extremely difficult the withdrawal of the valve assembly by outwardly directed movement once such assembly has been mounted or set up on the rim, but, at the same time, to constrain any inwardly directed movement thereof. In other words, the valve assembly of the present invention is additionally immune to being forced further inwardly once it has been mounted and appropriately fitted to the tire rim.
In fulfilment of the above-stated objects, a primary feature of the present invention resides in the provision of an enlarged head portion for the aforesaid rubber or elastomeric boot forming the valve assembly. This boot is also formed with a cylindrical skirt portion which is joined to the enlarged head portion by a narrowed neck portion. Moreover, the outer surface of the cylindrical skirt portion is normally in a conical configuration; that is, in the relaxed state for the rubber boot, the periphery of the skirt portion has a conical shape, whereas the interior surface defines a hollow cylinder. However, once the insert has been inserted into the boot from the opposite direction from which the boot was fitted into the rim, the outer conical portion of the boot is compelled to conform with the shape of the insert, the result being that the outer periphery also becomes cylindrical. The consequence which is of significance to the present invention is that the peripheral surface of the boot immediately abutting against the rim at the outside functions to prevent movement of the entire assembly inwardly. In other words, a groove is defined thereby with the desired effect that insertion of the insert precludes untoward inwardly directed movement of the valve assembly.
In addition to insuring that the entire assemly cannot be moved in an undesired manner so as to cause a breaking of the established seal or fit with the rim, the forcing inwardly of the insert establishes the desired seal at the interior of the boot portion; that is to say, the seal between the inner end of the insert and a spherical protrusion provided at the boot's inner end, thereby preventing any escape of air through the bore of the insert. However, by one form of device or another, the spherical protrusion can be manipulated when required so as to allow air to flow through suitably provided passageways in the boot portion and thence into the insert bore.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.